DS1 is stored in file: h5ex_d_extern.data
DS1:
 [  0 -1 -2 -3 -4 -5 -6 ]
 [  0  0  0  0  0  0  0 ]
 [  0  1  2  3  4  5  6 ]
 [  0  2  4  6  8 10 12 ]
